Cholestane-3ß,5α,6ß-Triol Inhibits Acid-Sensing Ion Channels and Reduces Acidosis-Mediated Ischemic Brain Injury.

BACKGROUND: Activation of the acid-sensing ion channels (ASICs) by tissue acidosis, a common feature of brain ischemia, contributes to ischemic brain injury, while blockade of ASICs results in protection. Cholestane-3ß,5α,6ß-triol (Triol), a major cholesterol metabolite, has been demonstrated as an endogenous neuroprotectant; however, the mechanism underlying its neuroprotective activity remains elusive. In this study, we tested the hypothesis that inhibition of ASICs is a potential mechanism. METHODS: The whole-cell patch-clamp technique was used to examine the effect of Triol on ASICs heterogeneously expressed in Chinese hamster ovary cells and ASICs endogenously expressed in primary cultured mouse cortical neurons. Acid-induced injury of cultured mouse cortical neurons and middle cerebral artery occlusion-induced ischemic brain injury in wild-type and ASIC1 and ASIC2 knockout mice were studied to examine the protective effect of Triol. RESULTS: Triol inhibits ASICs in a subunit-dependent manner. In Chinese hamster ovary cells, it inhibits homomeric ASIC1a and ASIC3 without affecting ASIC1ß and ASIC2a. In cultured mouse cortical neurons, it inhibits homomeric ASIC1a and heteromeric ASIC1a-containing channels. The inhibition is use-dependent but voltage- and pH-independent. Structure-activity relationship analysis suggests that hydroxyls at the 5 and 6 positions of the A/B ring are critical functional groups. Triol alleviates acidosis-mediated injury of cultured mouse cortical neurons and protects against middle cerebral artery occlusion-induced brain injury in an ASIC1a-dependent manner. CONCLUSIONS: Our study identifies Triol as a novel ASIC inhibitor, which may serve as a new pharmacological tool for studying ASICs and may also be developed as a potential drug for treating stroke.

Inhibition of ASIC1a Improves Behavioral Recovery after Stroke.

Stroke continues to be a leading cause of death and long-term disabilities worldwide, despite extensive research efforts. The failure of multiple clinical trials raises the need for continued study of brain injury mechanisms and novel therapeutic strategies for ischemic stroke. The contribution of acid-sensing ion channel 1a (ASIC1a) to neuronal injury during the acute phase of stroke has been well studied; however, the long-term impact of ASIC1a inhibition on stroke recovery has not been established. The present study sought to bridge part of the translational gap by focusing on long-term behavioral recovery after a 30 min stroke in mice that had ASIC1a knocked out or inhibited by PcTX1. The neurological consequences of stroke in mice were evaluated before and after the stroke using neurological deficit score, open field, and corner turn test over a 28 d period. ASIC1a knock-out and inhibited mice showed improved neurological scores more quickly than wild-type control and vehicle-injected mice after the stroke. ASIC1a knock-out mice also recovered from mobility deficits in the open field test more quickly than wild-type mice, while PcTX1-injected mice did not experience significant mobility deficits at all after the stroke. In contrast to vehicle-injected mice that showed clear-sidedness bias in the corner turn test after stroke, PcTX1-injected mice never experienced significant-sidedness bias at all. This study supports and extends previous work demonstrating ASIC1a as a potential therapeutic target for the treatment of ischemic stroke.